There has been a change in the direction of our army, and instead of “on to Richmond,” it has recently been “on to Petersburg.”

HEADQUARTERS ARMY OF THE POTOMAC,

Sunday, June 19.

The fourth day of the battle of Petersburg ended last night. If it shall open again to-day, it will be the siege of Petersburg, briefer, perhaps, than the battle.

We attacked three times yesterday—at 4 A. M., at noon, and at 4 P. M. Warren joined on the left and swung around with a skirmishing, front, half a mile at each advance, taking one line of works and pressing up to another, and the last. Hancock and Burnside in the centre found more opposition. The former has gained half a mile, the latter more. The loss in the last assault was particularly severe in Barlow’s and Gibbon’s division, and the 2d division of Burnside’s. Mill’s division, of the 6th corps, and Martindale’s division, of the 18th corps, swept up the river to within half a mile of the town. One more line and we have the town wholly circumvallated to its last defences.

Col. Chamberlain, commanding a brigade in the 5th corps, is wounded in the hip.

Capt. Byrd, of Barrow’s staff, received a hit in the thigh.

Col. Beaver, 148th Pennsylvania, in the side.

The Herald special, 19th A. M., says:—At 4 o’clock this A. M. Burnside’s corps attacked the enemy’s works on the left of our line, and carried them after a severe and protracted struggle, capturing about 500 prisoners, six excellent brass field pieces, and two that were spiked.

NEW YORK, June 21.—By Herald correspondence it appears Col. S. H. Mix, 3d N. Y. Cavalry, fell at the head of his brigade while charging the rebel works under Kautz, on the 15th. He would not let his men carry him off at the time and several attempts were subsequently made to recover his body.1